And finally, the last in our series of cloud storage services for PDF users (see part 1, part 2, & part 3).

There are many Cloud Storage Services available to make backups of your PDF files, but we’ve found that some services are better than others based on who you are and what you need in a cloud storage solution. Some services offer broad mobile access on a variety of platforms, and others do not. Some offer generous initial storage for free. Some index the PDF files for better searching.

Here’s a summary of the services, features, and our assessment of who each one is best for:

The nice thing about SkyDrive (aside from the largest initial free storage space) is that it is included with Windows 8, so there isn’t any additional setup required for Windows 8 users. If you recently acquired a new Windows 8 device, this is an easy place to start.

This is Google’s offering and may be a good choice if you already use Google’s other integrated applications like Gmail and Google Docs. Google Drive is also the only online service that indexes your PDF files so that they can be searched online. This means that you can search for content within the PDF files, and not just the file names. This alone makes it one of our favorites.

Dropbox was one of the first of the major online cloud storage services, so it has a large user base. The other major technology companies (Microsoft, Google, Amazon) seem to be catching up with better initial storage, but Dropbox is still widely used, especially among home users. Also, Dropbox just added an app for Windows 8 and Windows RT devices.

This service has the most comprehensive mobile offerings. Also, it has more flexibility for IT departments with a larger group of users that need to have centralized control and management of their accounts. It seems to be a popular choice for enterprise users, whereas some of the others are focused more on an individual user basis.

– free account with 50GB initial free storage; No mobile apps currently available

This is the newest entrant into this cloud storage market. It has a generous initial storage account and touts security and strong encryption as a main advantage. However, its security claims are controversial and the founder’s prior company was involved in some legal issues. We don’t recommend this service at the moment until we understand more about the technology and if the business looks both secure and stable.

– free email service with over 5GB (and growing) free storage; Android and iOS mobile apps, and also can be accessed with any mobile email client that supports IMAP.

Some organizations have firewalls that limit access to the other cloud-based storage solutions listed, but allows emailed PDFs to be sent through firewalls. Using Win2PDF’s email option and Gmail, you can still archive PDFs by just emailing copies to yourself. It also provides searchable index of PDF files that can be stored based on filters and labels you create.

* We like Gmail for the features, but other web-based email services (Outlook.com, Yahoo Mail, etc.) work similarly.

And of course, there’s always the option to use multiple services for redundancy or particular organizational needs.